1. Field of the Invention
Included are multiple component elastic fibers prepared by a solution-spinning process such as spandex spinning including polyurethaneurea and polyurethane compositions that have a cross-section including at least two separate regions with definable boundaries wherein at least one region defined by the boundaries of the cross-section includes a polyurethaneurea or polyurethane composition. One region of the fiber includes a fusibility improvement additive to enhance adhesion to itself or to a substrate.
2. Description of the Related Art
Polyurethane or polyurethane-urea (PU or PUU) elastomeric yarns can offer high stretch, good recovery from extension and good fit to the articles made from them, such as weft knit, warp knit, woven fabrics, nonwovens and other textiles. However, for articles containing PU or PUU elastomeric yarns, repeatedly stretching, scratching or cutting often cause problems of laddering, running and curling. These problems include a ladder-like crack and a gap may be generated, elastic yarns may slip out, grin, fray at cut edges and fabric curls may result, which damages the uniformity and appearance of articles. During cutting and sewing process, the phenomenon that PU or PUU elastomeric yarns pull away from seams under repeated extension easily takes place and leads to the loss in stretch of fabrics, which is so called “slip in” or seam slippage. Although such effects happen to elastomeric yarns except PU or PUU yarns, they are especially significant to PU or PUU elastomeric yarns due to their high stretch ability. Moreover, for some articles high steam or heat set efficiency is desired, especially hosiery applications.
Considerable efforts have been dedicated to develop thermal fusible and steam-settable PU or PUU elastomeric yarns. U.S. Patent Application Publication Nos. 2006/0030229A1 and 2008/0032580A1 discloses a type of highly fusible polyurethane elastic filament by melt spinning a polymer synthesized by reacting an isocyanate-terminated prepolymer prepared by the reaction of a polyol and a diisocyanate with a hydroxyl-terminated prepolymer prepared by the reaction of a polyol, a diisocyanate and a low-molecular-weight diol. This fusible PU filament has a melting point of 180° C. or below. Dry heat treatment at 150° C. for 45 seconds at 100% extension could make this PU filament fuse to each other or to other elastic or non-elastic filaments at crossover points. However, the low melting point of the PU filament yields unsatisfactory thermal resistance to creep under normal consumer applications which leads to garment bagging.
Improved spandex yarns are needed which will provide fusibility, steam-set capability during garment manufacturing, and superior stretch resilience to overcome one or more of the deficiencies of currently available fibers.